// Copyright 2008 The Closure Library Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS-IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

/**
 * @fileoverview Namespace with crypto related helper functions.
 */

goog.provide('goog.crypt');

goog.require('goog.array');


/**
 * Turns a string into an array of bytes; a "byte" being a JS number in the
 * range 0-255.
 * @param {string} str String value to arrify.
 * @return {Array.<number>} Array of numbers corresponding to the
 *     UCS character codes of each character in str.
 */
goog.crypt.stringToByteArray = function(str) {
  var output = [], p = 0;
  for (var i = 0; i < str.length; i++) {
    var c = str.charCodeAt(i);
    while (c > 0xff) {
      output[p++] = c & 0xff;
      c >>= 8;
    }
    output[p++] = c;
  }
  return output;
};


/**
 * Turns an array of numbers into the string given by the concatenation of the
 * characters to which the numbers correspond.
 * @param {Array} array Array of numbers representing characters.
 * @return {string} Stringification of the array.
 */
goog.crypt.byteArrayToString = function(array) {
  return String.fromCharCode.apply(null, array);
};


/**
 * Turns an array of numbers into the hex string given by the concatenation of
 * the hex values to which the numbers correspond.
 * @param {Array} array Array of numbers representing characters.
 * @return {string} Hex string.
 */
goog.crypt.byteArrayToHex = function(array) {
  return goog.array.map(array, function(numByte) {
    var hexByte = numByte.toString(16);
    return hexByte.length > 1 ? hexByte : '0' + hexByte;
  }).join('');
};


/**
 * Converts a JS string to a UTF-8 "byte" array.
 * @param {string} str 16-bit unicode string.
 * @return {Array.<number>} UTF-8 byte array.
 */
goog.crypt.stringToUtf8ByteArray = function(str) {
  // TODO(user): Use native implementations if/when available
  str = str.replace(/\r\n/g, '\n');
  var out = [], p = 0;
  for (var i = 0; i < str.length; i++) {
    var c = str.charCodeAt(i);
    if (c < 128) {
      out[p++] = c;
    } else if (c < 2048) {
      out[p++] = (c >> 6) | 192;
      out[p++] = (c & 63) | 128;
    } else {
      out[p++] = (c >> 12) | 224;
      out[p++] = ((c >> 6) & 63) | 128;
      out[p++] = (c & 63) | 128;
    }
  }
  return out;
};


/**
 * Converts a UTF-8 byte array to JavaScript's 16-bit Unicode.
 * @param {Array.<number>} bytes UTF-8 byte array.
 * @return {string} 16-bit Unicode string.
 */
goog.crypt.utf8ByteArrayToString = function(bytes) {
  // TODO(user): Use native implementations if/when available
  var out = [], pos = 0, c = 0;
  while (pos < bytes.length) {
    var c1 = bytes[pos++];
    if (c1 < 128) {
      out[c++] = String.fromCharCode(c1);
    } else if (c1 > 191 && c1 < 224) {
      var c2 = bytes[pos++];
      out[c++] = String.fromCharCode((c1 & 31) << 6 | c2 & 63);
    } else {
      var c2 = bytes[pos++];
      var c3 = bytes[pos++];
      out[c++] = String.fromCharCode(
          (c1 & 15) << 12 | (c2 & 63) << 6 | c3 & 63);
    }
  }
  return out.join('');
};